U.S. patent number 10,626,229 [Application Number 14/868,002] was granted by the patent office on 2020-04-21 for silane-crosslinkable ethylene-propylene copolymer and crosslinked body of the same.
This patent grant is currently assigned to FURUKAWA ELECTRIC CO., LTD., FURUKAWA ELECTRIC POWER SYSTEMS CO., LTD.. The grantee listed for this patent is FURUKAWA ELECTRIC CO., LTD., FURUKAWA ELECTRIC POWER SYSTEMS CO., LTD.. Invention is credited to Hironobu Hirano, Jae Kyung Kim, Eiji Kozawa, Yasuo Nakajima, Yutaka Suzuki, Masami Tazuke.
![](/patent/grant/10626229/US10626229-20200421-M00001.png)
United States Patent |
10,626,229 |
Kim , et al. |
April 21, 2020 |
Silane-crosslinkable ethylene-propylene copolymer and crosslinked
body of the same
Abstract
A polyolefin-based thermoplastic elastomer and a crosslinked
body of the same which can undergo a silane-crosslinking process
excellent in productivity and have a rubber property required as a
substitute material for EPDM is disclosed herein and can use a
silane-crosslinkable ethylene-propylene copolymer characterized in
that an organic peroxide (B) and a silane coupling agent (C) are
compounded with an ethylene-propylene copolymer resin (A) which
comprises 5 to 25% by mass of an ethylene component and 75 to 95%
by mass of a propylene component, and whose MFR measured at
230.degree. C. and with a load of 2.16 kg applied is 20.0 g/10 min
or less. and further a compounded amount of the organic peroxide is
0.1 to 0.6 pts. mass based on 100 pts. mass of the
ethylene-propylene copolymer resin (A) and a one-minute half-life
temperature of the organic peroxide is 175.2.degree. C. or
less.
Inventors: |
Kim; Jae Kyung (Tokyo,
JP), Kozawa; Eiji (Tokyo, JP), Tazuke;
Masami (Tokyo, JP), Nakajima; Yasuo (Tokyo,
JP), Suzuki; Yutaka (Tokyo, JP), Hirano;
Hironobu (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
FURUKAWA ELECTRIC CO., LTD.
FURUKAWA ELECTRIC POWER SYSTEMS CO., LTD. |
Tokyo
Yokohama-shi |
N/A
N/A |
JP
JP |
|
|
Assignee: |
FURUKAWA ELECTRIC CO., LTD.
(Tokyo, JP)
FURUKAWA ELECTRIC POWER SYSTEMS CO., LTD. (Yokohama-shi,
JP)
|
Family
ID: |
51623518 |
Appl.
No.: |
14/868,002 |
Filed: |
March 6, 2014 |
PCT
Filed: |
March 06, 2014 |
PCT No.: |
PCT/JP2014/055724 |
371(c)(1),(2),(4) Date: |
September 28, 2015 |
PCT
Pub. No.: |
WO2014/156529 |
PCT
Pub. Date: |
October 02, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160046770 A1 |
Feb 18, 2016 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 29, 2013 [JP] |
|
|
2013-072292 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L
23/142 (20130101); C08L 51/06 (20130101); C08F
255/04 (20130101); C08J 3/24 (20130101); C08K
3/26 (20130101); C08L 23/142 (20130101); C08L
2312/08 (20130101); C08F 255/04 (20130101); C08F
230/08 (20130101); C08K 2003/265 (20130101); C08L
2312/08 (20130101); C08J 2323/26 (20130101) |
Current International
Class: |
C08L
51/04 (20060101); C08L 23/14 (20060101); C08F
255/04 (20060101); C08K 3/26 (20060101); C08L
51/06 (20060101); C08J 3/24 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
4034 |
|
Sep 1979 |
|
EP |
|
54-117549 |
|
Sep 1979 |
|
JP |
|
55-129441 |
|
Oct 1980 |
|
JP |
|
57-147507 |
|
Sep 1982 |
|
JP |
|
58-206659 |
|
Dec 1983 |
|
JP |
|
63-172712 |
|
Jul 1988 |
|
JP |
|
06-136066 |
|
May 1994 |
|
JP |
|
WO-2010/009024 |
|
Jan 2010 |
|
WO |
|
Other References
https://www.united-initiators.com/wp-content/uploads/2016/07/UI_Brochure_C-
UROX.pdf; date unknown. cited by examiner .
International Search Report (with English translation),
International Application No. PCT/JB2014/055724, dated May 27,
2014. cited by applicant .
Varox Peroxide Brochure, Crosslinking Agents for the Rubber &
Plastics Industries, available at
<http://www.camsi-x.com/web/Por_Mercado/VAROX_Peroxides_Brochure.pdf&g-
t;. cited by applicant .
Chemicalland 21--Di-tert-BUTYL Peroxide available at
<http://www.chemicalland21.com/specialtychem/perchem/DI-tert-BUTYL%20P-
EROXIDE.htm>. cited by applicant .
International Preliminary Report on Patentability, corresponding
International Application No. PCT/JP2014/055724, dated Sep. 29,
2015. cited by applicant .
Written Opinion of the International Searching Authority (English
Translation), for International Application No. PCT/JP2014/055724,
dated May 27, 2014. cited by applicant.
|
Primary Examiner: Yoon; Tae H
Attorney, Agent or Firm: Marshall, Gerstein & Borun
LLP
Claims
What is claimed is:
1. A crosslinked body for connecting electric cables, comprising: a
cross-linked silane-crosslinkable ethylene-propylene graft
copolymer containing an insulating inorganic filler, the
cross-linked silane-crosslinkable ethylene-propylene graft
copolymer being obtained by crosslinking a silane-crosslinkable
ethylene-propylene graft copolymer having the insulating inorganic
filler incorporated therein during a graft modification, wherein
the silane-crosslinkable ethylene-propylene graft copolymer having
the insulating inorganic filler incorporated therein during the
graft modification is obtained by compounding an organic peroxide
(B), a silane coupling agent selected from vinyl trimethoxysilane
and/or vinyl triethoxysilane (C), and the insulating inorganic
filler (D) with an ethylene-propylene random copolymer resin (A),
wherein the ethylene-propylene random copolymer resin has an
isotactic structure, an ethylene component and a propylene
component being 5 to 25% by mass and 75 to 95% by mass,
respectively, and a melt mass flow rate measured at 230.degree. C.
and with a load of 2.16 kg applied is 20.0 g/10 min or less,
wherein the organic peroxide (B) is present in an amount of 0.1 to
0.6 pts. mass based on 100 pts. mass of the ethylene-propylene
copolymer resin (A) and a one-minute half-life temperature of the
organic peroxide (B) is between 150.degree. C. and 166.degree. C.,
wherein the crosslinked body has a heat deformation ratio of 35% or
less which indicates a reduction rate X % determined by a formula
X=(t.sub.0-t.sub.1)/t.sub.0*100, where t.sub.0 denotes thickness of
a test piece before heating and t.sub.1 denotes thickness thereof
after heating, the thickness t.sub.1 being determined in such a
manner that the test piece is made into a rectangular shape that is
2 mm thick, 15 mm wide, and 30 mm long, and after heating the test
piece at 100.degree. C. for 30 min., a load of 2.0 kg is applied to
the test piece, followed by further heating the test piece at the
same temperature for 30 min. and thereafter the thickness t.sub.1
is measured, so that the thickness t.sub.1 is obtained, and an AC
dielectric breakdown strength of the crosslinked body is 25 kV/mm
or more which is determined by a formula AC dielectric breakdown
strength (kV/mm)=AC dielectric breakdown voltage (kV)/thickness of
test piece (mm), obtained by the following procedure: according to
JIS C2110-1 electrodes are set at an approximately central portion
of a test piece of 1 mm thick between upper and lower portions of
the test piece, an AC voltage is boosted from 0V at a constant rate
(1 kV/10 min.) and an AC breakdown voltage is measured.
2. A crosslinked body for connecting electric cables, comprising: a
cross-linked silane-crosslinkable ethylene-propylene graft
copolymer containing an insulating inorganic filler, the
cross-linked silane-crosslinkable ethylene-propylene graft
copolymer being obtained by crosslinking a silane-crosslinkable
ethylene-propylene graft copolymer having the insulating inorganic
filler incorporated therein during a graft modification, wherein
the silane-crosslinkable ethylene-propylene graft copolymer having
the insulating inorganic filler incorporated therein during the
graft modification is obtained by compounding an organic peroxide
(B), a silane coupling agent selected from vinyl trimethoxysilane
and/or vinyl triethoxysilane (C), and the insulating inorganic
filler (D) with an ethylene-propylene random copolymer resin (A),
wherein the ethylene-propylene random copolymer resin has an
isotactic structure, an ethylene component and a propylene
component being 5 to 25% by mass and 75 to 95% by mass,
respectively, and a melt mass flow rate measured at 230.degree. C.
and with a load of 2.16 kg applied is 20.0 g/10 min or less,
wherein the organic peroxide (B) is present in an amount of 0.1 to
0.6 pts. mass based on 100 pts. mass of the ethylene-propylene
copolymer resin (A) and a one-minute half-life temperature of the
organic peroxide (B) is between 150.degree. C. and 166.degree. C.,
wherein the crosslinked body has a residual strain ratio of 60% or
less which is determined by a formula
(l.sub.1-l.sub.0)/l.sub.0*100, where l.sub.1 denotes a length of a
test piece after applying tension thereto and l.sub.0 denotes a
length thereof before applying tension thereto, the length l.sub.1
being determined in such a manner that the test piece is made into
a rectangular shape that is 2 mm thick, 10 mm wide, and 50 mm long
except for a length of grippers, and after putting the test piece
into a test machine heated at 90.degree. C. to heat the test piece
for 5 minutes therein, the test piece is extended at a tension rate
of 50 mm/min. till its strain ratio reaches 250% and immediately
after that, the test piece thus extended is turned back to normal
at the rate of 50 mm/min. and at the moment a stress caused by the
extending action becomes zero, a distance of the test piece between
grippers is measured, so that the length l.sub.1 is obtained from
the distance, an AC dielectric breakdown strength of the
crosslinked body is 25 kV/mm or more which is determined by a
formula AC dielectric breakdown strength (kV/mm)=AC dielectric
breakdown voltage (kV)/thickness of test piece (mm), obtained by
the following procedure: according to JIS C2110-1 electrodes are
set at an approximately central portion of a test piece of 1 mm
thick between upper and lower portions of the test piece, an AC
voltage is boosted from 0V at a constant rate (1 kV/10 min.) and an
AC breakdown voltage is measured.
3. The crosslinked body according to claim 1, wherein a compounded
amount of the silane coupling agent (C) is 1 to 5 pts. mass based
on 100 pts. mass of the ethylene-propylene copolymer resin (A).
4. The crosslinked body of claim 1, further comprising a
softener.
5. The crosslinked body according to claim 1, wherein a compounded
amount of the insulating inorganic filler is 10 to 150 pts. mass
based on 100 pts. mass of the silane-crosslinkable
ethylene-propylene graft copolymer.
6. The crosslinked body according to claim 4, wherein a compounded
amount of the softener is 5 to 50 pts. mass based on 100 pts. mass
of the insulating inorganic filler.
7. The crosslinked body according to claim 2, wherein a compounded
amount of the silane coupling agent (C) is 1 to 5 pts. mass based
on 100 pts. mass of the ethylene-propylene copolymer resin (A).
8. The crosslinked body of claim 2, further comprising a
softener.
9. The crosslinked body according to claim 8, wherein a compounded
amount of the softener is 5 to 50 pts. mass based on 100 pts. mass
of the insulating inorganic filler.
10. The crosslinked body according to claim 2, wherein a compounded
amount of the insulating inorganic filler is 10 to 150 pts. mass
based on 100 pts. mass of the silane-crosslinkable
ethylene-propylene graft copolymer.
11. The crosslinked body of claim 1, wherein a dielectric breakdown
is generated beyond 360 minutes obtained by the following
procedure: according to JIS C2136, a contaminating liquid (ammonia
water) is started to be supplied (0.3 ml/min.) onto the surface of
a test piece of 50 mm*120 mm*6 mm and with the contaminating liquid
allowed to flow constantly thereonto, a voltage is boosted up to
3.5 kV to measure a time required to cause its dielectric
breakdown.
12. The crosslinked body according to claim 11, wherein a
compounded amount of the insulating inorganic filler is in the
range of 50 to 100 pts. mass, based on 100 pts. mass of the
ethylene-propylene copolymer resin (A).
13. The crosslinked body according to claim 12, wherein the AC
dielectric breakdown strength is 27.6 kV/mm or more which is
determined by a formula AC dielectric breakdown strength (kV/mm)=AC
dielectric breakdown voltage (kV)/thickness of test piece (mm),
obtained by the following procedure: according to JIS C2110-1
electrodes are set at an approximately central portion of a test
piece of 1 mm thick between upper and lower portions of the test
piece, an AC voltage is boosted from 0V at a constant rate (1 kV/10
min.) and an AC breakdown voltage is measured.
14. The crosslinked body of claim 2, wherein a dielectric breakdown
is generated beyond 360 minutes obtained by the following
procedure: according to JIS C2136, a contaminating liquid (ammonia
water) is started to be supplied (0.3 ml/min.) onto the surface of
a test piece of 50 mm*120 mm*6 mm and with the contaminating liquid
allowed to flow constantly thereonto, a voltage is boosted up to
3.5 kV to measure a time required to cause its dielectric
breakdown.
15. The crosslinked body according to claim 14, wherein a
compounded amount of the insulating inorganic filler is in the
range of 50 to 100 to pts. mass, based on 100 pts. mass of the
ethylene-propylene copolymer resin (A).
16. The crosslinked body according to claim 15, wherein the AC
dielectric breakdown strength is 27.6 kV/mm or more which is
determined by a formula AC dielectric breakdown strength (kV/mm)=AC
dielectric breakdown voltage (kV)/thickness of test piece (mm),
obtained by the following procedure: according to JIS C2110-1
electrodes are set at an approximately central portion of a test
piece of 1 mm thick between upper and lower portions of the test
piece, an AC voltage is boosted from 0V at a constant rate (1 kV/10
min.) and an AC breakdown voltage is measured.
17. The crosslinked body according to claim 1, wherein a compounded
amount of insulating inorganic filler is in a range of 100 to 150
pts mass based on 100 pts mass of the ethylene-propylene copolymer
resin(A).
18. The crosslinked body according to claim 2, wherein a compounded
amount of insulating inorganic filler is in a range of 100 to 150
pts mass based on 100 pts mass of the ethylene-propylene copolymer
resin(A).
19. The crosslinked body according to claim 17, wherein the AC
dielectric breakdown strength of the crosslinked body is 30.2 kV/mm
or more which is determined by a formula AC dielectric breakdown
strength (kV/mm)=AC dielectric breakdown voltage (kV)/thickness of
test piece (mm), obtained by the following procedure: according to
JIS C2110-1 electrodes are set at an approximately central portion
of a test piece of 1 mm thick between upper and lower portions of
the test piece, an AC voltage is boosted from 0V at a constant rate
(1 kV/10 min.) and an AC breakdown voltage is measured.
20. The crosslinked body according to claim 18, wherein the AC
dielectric breakdown strength of the crosslinked body is 30.2 kV/mm
or more which is determined by a formula AC dielectric breakdown
strength (kV/mm)=AC dielectric breakdown voltage (kV)/thickness of
test piece (mm), obtained by the following procedure: according to
JIS C2110-1 electrodes are set at an approximately central portion
of a test piece of 1 mm thick between upper and lower portions of
the test piece, an AC voltage is boosted from 0V at a constant rate
(1 kV/10 min.) and an AC breakdown voltage is measured.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application is a continuation of International
Application No. PCT/JP2014/055724 filed Mar. 6, 2014, which claims
the priority benefit of Japanese Patent Application No. 2013-072292
filed Mar. 29, 2013, the disclosure of which are hereby
incorporated by reference in their entireties.
FIELD OF THE DISCLOSURE
The present disclosure relates to a silane-crosslinkable
ethylene-propylene copolymer and a crosslinked body of the same
which are a resin material excellent in formability, workability,
machinability, an insulating property, and particularly a rubber
property and are usable as a substituting material for a rubber
material including EDPM.
BACKGROUND
In the field of parts for connecting electric cables or the like,
EPDM (crosslinked rubber of ethylene-propylene-diene ternary
copolymer) is frequently used. This is attributable to a recovery
property after tension applied thereto, a rubber property such as
flexibility, an insulating property, an electric property such as a
tracking resistance property, a heat resistance property, a
long-term property such as heat aging resistance, and such a
superior property as a high degree of freedom for a composition for
the sake of corresponding flexibly to levels demanded for the above
properties. These EDPMs are produced by a crosslinking process
through processes using peroxides and sulfuric compounds together
(this process is generally called as "vulcanizing process" in
rubber). This vulcanizing process requires a long time in
manufacturing to lower its productivity, causing its manufacturing
cost to be substantially pushed up.
In order to solve these problems, a study for manufacturing
products of EDPM by a mold injection process is on-going and the
manufacturing is put to practical use. Nevertheless, the
vulcanizing process inside a metallic mold is still needed. There
is further a problem that when manufacturing a multi-layered molded
object, an interlayer adhesive property is poor. Hence, the
improvement in productivity is limited since a surface treatment
should be carried out for every layer to need to improve the
adhesive property and so on. Further, there is a problem that a
composition study for improving fluidity such as adding a
developing oil in the composition must be newly performed. In the
field of the parts for connecting the electric cables, e.g., there
is a case where properties (an electric property) required for the
products are impaired, and a phenomenon such as the oil
transferring to other layers occur, thus causing a new problem in
reliabilities of processing and products.
As a resolution method for these problems, it is considered that a
thermoplastic elastomer, e.g., is used. As substitute for EPDM, a
polyolefin-based thermoplastic elastomer is most suitable and the
elastomer, which does not need the vulcanizing process differently
from EDPM and has such a grade of commercial products as is usable
for any one of extrusion, injection, and molding methods, is
available in the market. A polyolefin-based thermoplastic elastomer
material is classified roughly into two types from its makeup of
components. One type includes a crosslinked body of rubber acting
as a dispersion phase in a thermoplastic resin serving as a matrix.
The other type is an olefin-based copolymer whose crystallinity is
intendedly lessened. In both the elastomer materials, however,
their physical properties widely vary near their melting points and
besides a plastic property remains at a normal operating
temperature range. Therefore, since there are some cases where
their recovery actions are poor after deformation, a necking
phenomenon occurs after large deformation and so on, both the
elastomer materials cannot exert a property suitable to that of
rubber, so that there exists no elastomer material with a
satisfactory property as substitute for rubber.
In order to make up for such a lack of the rubber property, the
crosslinking process is on-going for the elastomer. There are
generally three crosslinking methods including a peroxide
crosslinking one, a silane crosslinking one, and a radiation
crosslinking one (see a patent document 1). However, the
crosslinking method using peroxide is the same method as that for
manufacturing EDPM and the manufacturing flow involves the
crosslinking process, and therefore the purpose for improving the
productivity cannot be achieved. Further, although the crosslinking
method using radiation is advantageous from the viewpoint of
capable of readily obtaining a crosslinked body, a radiation
irradiating system is extremely high in price to considerably push
up the manufacturing cost of the crosslinked body, thus becoming
unsuitable to practical use.
It is known that in the silane crosslinking method, a process for
carrying out a silane modification of the thermoplastic elastomer
while maintaining a suitable rubber property is extremely
difficult. This is because a polyolefin-based thermoplastic
elastomer excellent in rubber property is easy to be subjected to
radical decomposition and hence the resin in which a
crosslinkability and the rubber property are compatible is hard to
obtain. The reason for this is that the olefin-based thermoplastic
elastomer commonly known is not composed of a single component, but
there are many elastomers blended with heterogeneous components. As
cited above, as a representative one, there is an elastomer
material using a resin (polypropylene) easy to decompose as a
matrix and containing, in a dispersion phase, a crosslinkable resin
such as crosslinked EPDM. At the time of manufacturing, such an
elastomer is allowed to undergo a crosslinking reaction and a
decomposing reaction to develop the rubber property in a
delicately-balanced state. Accordingly, when such an elastomer
further undergoes the silane modification process, a
physical-property balance is broken down and hence a crosslinked
body meeting a condition of being ought to be a substitute for EDPM
cannot be obtained.
Then, when using, as a thermoplastic elastomer, an
ethylene-propylene copolymer whose propylene component is increased
for the purpose of lowering a degree of crystallinity, if achieving
an ideal crosslinking condition, the ethylene-propylene copolymer
is optimal as a substitute. There are, however, plenty of
decomposable propylene components therein and hence this copolymer
is considerably decomposed in a process for applying a graft
reaction to a silane coupling agent to become thereby unable to
maintain the rubber property. For this reason, a physical property
substitutable for EPDM is extremely difficult to develop.
Accordingly, when trying to manufacture a superior silane
crosslinked body using such a common thermoplastic elastomer, the
resin itself needs to review, resulting in a high material cost.
This is why there exists no low-price commercialized products under
the present circumstances.
Also, International Patent Application Publication No. WO
2010/009024 discloses such an ethylene-propylene copolymer,
excellent in a heat shielding performance, subjected to the
radiation crosslinking process. However, a silane-crosslinked
ethylene-propylene copolymer which develops a superior rubber
property and is subjected to a silane crosslinking process is not
disclosed therein.
SUMMARY
The present disclosure is made to solve the problems like these.
Therefore, it is an object of the present disclosure to provide a
polyolefin-based thermoplastic elastomer and a crosslinked body of
the same which can undergo the silane crosslinking process
excellent in productivity and have a rubber property required as
substitute for EDPM.
In order to achieve the above object, there is provided the
following embodiments.
(1) A crosslinked body, wherein the crosslinked body is obtained by
crosslinking the silane-crosslinkable ethylene-propylene graft
copolymer, wherein an organic peroxide (B) and a silane coupling
agent selected from vinyl trimethoxysilane and/or vinyl
triethoxysilane (C) are compounded with an ethylene-propylene
random copolymer resin (A) which comprises substantially an
ethylene component and a propylene component has an isotactic
structure, the ethylene component and the propylene component being
5 to 25% by mass and 75 to 95% by mass, respectively, and whose
melt mass flow rate measured at 230.degree. C. and with a load of
2.16 kg applied is 20.0 g/10 min or less, and further a compounded
amount of the organic peroxide (B) is 0.1 to 0.6 pts. mass based on
100 pts. mass of the ethylene-propylene copolymer resin (A) and a
one-minute half-life temperature of the organic peroxide (B) is
between 130.degree. C. and 175.2.degree. C., wherein a heat
deformation ratio is 35% or less which indicates a reduction rate X
% determined by a formula X=(t.sub.0-t.sub.1)/t.sub.0*100, where
t.sub.0 denotes thickness of a test piece before heating and
t.sub.1 denotes thickness thereof after heating, the thickness
t.sub.1 being determined in such a manner that the test piece is
made into a rectangular shape that is 2 mm thick, 15 mm wide, and
30 mm long, and after heating the test piece at 100.degree. C. for
30 min., a load of 2.0 kg/f is applied to the test piece, followed
by further heating the test piece at the same temperature for 30
min. and thereafter the thickness t.sub.1 is measured, so that the
thickness t.sub.1. is obtained.
(2) A crosslinked body, wherein the crosslinked body is obtained by
crosslinking the silane-crosslinkable ethylene-propylene graft
copolymer, wherein an organic peroxide (B) and a silane coupling
agent selected from vinyl trimethoxysilane and/or vinyl
triethoxysilane (C) are compounded with an ethylene-propylene
random copolymer resin (A) which comprises substantially an
ethylene component and a propylene component has an isotactic
structure, the ethylene component and the propylene component being
5 to 25% by mass and 75 to 95% by mass, respectively, and whose
melt mass flow rate measured at 230.degree. C. and with a load of
2.16 kg applied is 20.0 g/10 min or less, and further a compounded
amount of the organic peroxide (B) is 0.1 to 0.6 pts. mass based on
100 pts. mass of the ethylene-propylene copolymer resin (A) and a
one-minute half-life temperature of the organic peroxide(B) is
between 130.degree. C. and 175.2.degree. C., wherein a residual
strain ratio is 60% or less which is determined by a formula
(l.sub.1-l.sub.0)/l.sub.0*100, where l.sub.1 denotes a length of a
test piece after applying tension thereto and l.sub.0 denotes a
length thereof before applying tension thereto, the length l.sub.1
being determined in such a manner that the test piece is made into
a rectangular shape that is 2 mm thick, 10 mm wide, and 50 mm long
except for a length of grippers, and after putting the test piece
into a test machine heated at 90.degree. C. to heat the test piece
for 5 minutes therein, the test piece is extended at a tension rate
of 50 mm/min. till its strain ratio reaches 250% and immediately
after that, the test piece thus extended is turned back to normal
at the rate of 50 mm/min. and at the moment a stress caused by the
extending action becomes zero, a distance of the test piece between
grippers is measured, so that the length l.sub.1 is obtained from
the distance.
(3) The crosslinked body according to (1) or (2), wherein a
compounded amount of the silane coupling agent (C) is 1 to 5 pts.
mass based on 100 pts. mass of the ethylene-propylene copolymer
resin (A).
(4) The crosslinked body, wherein the crosslinked body is obtained
by crosslinking the composition wherein the silane-crosslinkable
ethylene-propylene graft copolymer according to (1) or (2) contains
an insulating inorganic filler.
(5) The crosslinked body, wherein the crosslinked body is obtained
by crosslinking the composition according to (4) further contains a
softener.
(6) The crosslinked body according to (4), wherein a compounded
amount of the insulating inorganic filler is 10 to 150 pts. mass
based on 100 pts. mass of the silane-crosslinkable
ethylene-propylene graft copolymer.
(7) The crosslinked body according to (4), wherein a compounded
amount of the softener is 5 to 50 pts. mass based on 100 pts. mass
of the insulating inorganic filler.
There can be provided the polyolefin-based thermoplastic elastomer
and the crosslinked body of the same which can undergo a silane
crosslinking process excellent in productivity and have the rubber
property required as a substitute for EDPM.
DETAILED DESCRIPTION
Hereunder is a detailed description on embodiments of the present
disclosure.
Base Resin
As a base resin of the silane crosslinked body according to the
present disclosure, an ethylene-propylene random copolymer is used
which is uniformed in active site and is polymerized using a single
site catalyst represented by a catalyst generally called a
metallocene-based catalyst. In these copolymers, a structure of a
propylene component mainly involves an isotactic structure.
In the general isostatic polymerization method, the polymerization
is carried out in the presence of a catalyst containing a
bis(cyclopentadienyl) metallic compound and (1) a non-coordinating
compatible anion activator or (2) an alumoxane activator. Here, the
bis(cyclopentadienyl) metallic compound means a compound which
contains group IV transition metals (titanium, zirconium, hafnium)
as a central metal and as a ligand, two cyclopentadienyls
crosslinked by a substituted or non-substituted carbon atom or a
substituted or non-substituted silicon atom and in which the group
IV transition metal compound is chiral. Further, a crosslinking
atom is substituted by at least one methyl group and a
cyclopentadienyl ligand is desirably indenyl. The non-coordinating
compatible anion activator (1) is a precursor ionic compound (a
boron-based anion promotor) containing group XIII anion substituted
by tetraaryl halide in which an aryl substituent has at least two
cyclic aromatic rings. Further, the alumoxane activator (2) is
desirably methyl alumoxane that is a reactant of trimethylaluminum
and water. The chemical formula is expressed by the following one.
CH.sub.3--(Al(CH.sub.3)--O)n--Al(CH.sub.3)--CH.sub.3(n=4.about.20)
Chemical Formula 1
The ethylene-propylene random copolymer usable appropriately in the
present disclosure is manufactured by copolymerizing propylene and
ethylene at reaction temperature of 60.degree. C. or more in a
solution method, using a catalyst complex containing the
bis(cyclopentadienyl) metallic compound and the non-coordinating
compatibility anion activator (1) or the alumoxane activator (2).
At this time, the propylene becomes a stereospecific polypropylene
by the catalyst complex. This resin containing a propylene
component as a principal component and substantially containing no
other monomer component than the propylene component and the
ethylene component exhibits an excellent physical property balance
since this resin has the homogeneity of polymer chains and an
advanced stereoregularity.
Further, due to the property of its manufacturing method, the
ethylene-propylene copolymer thus obtained becomes one
substantially containing no nonhomogeneity in its intermolecular
composition distribution. Specifically, this copolymer becomes one
whose intermolecular composition distribution is extremely high in
random property, thus becoming a resin with a superior rubber
property as described in detail later. This tendency becomes more
prominent by allowing this resin to undergo a silane crosslinking
process.
As the base resin optimally usable for the silane-crosslinked body
according to the present disclosure, the random copolymer as
described above is most desirable to be easy to obtain a target
rubber property. There is, however, no need for limiting this base
resin, and it may be allowable to use a resin partially having a
block structure of the ethylene component or the propylene
component to allow an intermolecular heterogeneous property to
exist.
Further, in the resin used for the present disclosure, a content of
the propylene component is desirably in the range of 75 to 95% by
mass. If the content is less than 75% by mass, a crystallinity of
the resin becomes poor and even if the resin is solidified by a
cooling operation, it is difficult to make the resin into a stable
shape. Therefore, the resin cannot be taken off in a strand-like
shape after extrusion to become unable to perform a cutting process
(a pelletization process) into a pellet shape, thereby presenting
inconvenience to the next molding process. Further, for the same
reason, a master batch into which an additive agent is kneaded in
advance cannot be manufactured. If the silane crosslinked body is
manufactured using such a material, the material needs to be made
into a product shape by a molding machine equipped with special
equipment. Specifically, after once manufacturing a
silane-crosslinkable resin by an extruder, the resin is taken off
in a sheet-like shape and then after the resin thus shaped is put
into a banbury mixer or he like to be mixed with necessary additive
agent, the mixture is allowed to undergo local processes to be made
again into a sheet-like shape, further making it necessary to
transfer the sheet-like matter to a molding machine. As a result,
the productivity is remarkably lowered as compared with a case
where its pelletization is possible. On the other hand, when the
propylene component exceeds 95% by mass, the crystallinity of the
propylene component is too high, a lack in elastomeric property
results. Accordingly, even if allowing the resin to undergo a
crosslinking process, a rubber-like property cannot be obtained and
therefore the object of the present disclosure cannot be attained.
For the above reason, the content of the propylene component is
desirably in the range of 75 to 95% by mass and is more desirably
in the range of 75 to 85% by mass.
The fact that the resin is substantially composed of the ethylene
propylene component and the propylene component means that the
ethylene-propylene copolymer resin (A) is composed of the ethylene
propylene component, the propylene component, and inevitable
impurities. Desirably, the impurities contained in the
ethylene-propylene copolymer resin (A) are 1% by mass or less and
the total of the ethylene propylene component and propylene
component is 99% by mass or more.
Organic Peroxide
As a radical generator, since the decomposition of the base resin
becomes problematic in the present base, the radical generator
whose one-minute half-life temperature is 176.degree. C. or less is
used. A radical generator whose one-minute half-life temperature is
130.degree. C. to 176.degree. C. is desirable, and a radical
generator whose one-minute half-life temperature is 130 to
175.2.degree. C. is more desirable, and a radical generator whose
one-minute half-life temperature is 150 to 166.degree. C. is
furthermore desirable. If using a radical generator whose
one-minute half-life temperature exceeds this range is used, the
radical generator does not sufficiently advance in decomposition
and thereby a graft reaction stops advancing. When increasing an
extrusion temperature in order to ought to improve this problem,
the decomposition of the base resin drastically progresses to
become unable to obtain a crosslinked body for attaining a target
degree of crosslinking. Further, if using the radical generator
with the one-minute half-life temperature less than this range, the
decomposition has advanced at a comparatively early stage of the
extrusion to complete the reaction under an insufficient kneading
condition. Thus, since the graft becomes insufficient, the graft
concentration becomes non-uniform inside the system and so on, a
crosslinked body that varies widely is finally manufactured.
As the radical generators suitable to such conditions, for example
the following organic peroxides are cited: dibenzoyl peroxide;
peroxy-di(3-methylbenzoyl); peroxy-benzoyl(3-methylbenzoyl);
disuccinic acid peroxide; peroxy-2-ethylhexane acid-t-hexyl;
peroxy-2-ethylhexanoic acid-t-butyl; peroxy-2 methylcyclohexanoic
acid 1,1-di(t-butyl); peroxy-3,3,5-trimethylcyclohexanoic
acid-1,1-di(t-hexyl); peroxy-cyclohexanoic acid 1,1-di(t-hexyl);
peroxy-cyclohexanoic acid 1,1-(t-butyl);
2,2-di(peroxy-cyclohexanoic acid 4,4-di(t-butyl)) propane;
peroxy-isopropylmonocarboxylic acid t-hexyl;
2,5-dimethyl-2,5-di(benzoylperoxy)hexane;
peroxy-isopropylmonocarboxylic acid t-butyl; peroxy-lauric acid
t-butyl; peracetic acid-t-butyl; peroxy-benzene acid t-hexyl;
peroxy-2-ethylhexylmonocarboxylic acid t-butyl;
peroxy-3,5,5-trimethylhexanoic acid t-butyl; peroxy-benzene acid
t-butyl; monopermaleic acid t-butyl; 4,4-bis[(t-butyl)
peroxy]pentanoic acid butyl; peroxy-cumene acid t-butyl; dicumyl
peroxide; and di(2-t-butylperoxyisopropyl)benzene.
A compounded amount of the radical generator depends on a type of
radical generator and an existing amount of an additive agent with
a radical trapping function. The compounded amount is, however,
desirably 0.1 to 0.6 pts. mass based on 100 pts. mass of the resin.
If the compounded amount is less than this compounded amount, an
absolute amount of the radical generated in a system is too small
to advance adequately a reaction and hence a sufficient rubber
property is unable to be obtained after the crosslinking process.
Contrarily, if the compounded amount is more than this amount, an
amount of the radical generated in the system is too large, and
hence the decomposition of the base resin advances too much, and
thereby even if a sufficient crosslinking degree is attained by the
crosslinking process, the base resin is severely deteriorated to
make it impossible to obtain an excellent mechanical property.
The one-minute half-life temperature described above is measured by
the following method. By using a solvent, such as benzene, low in
activation level to a radical, a solution of an organic peroxide of
0.1 mol/L is prepared. The solution is encapsulated into a glass
tube subjected to nitrogen substitution to be immersed in a
constant-temperature reservoir set at a given temperature and then
the solution is thermally decomposed. The decomposing action of the
organic peroxide in a dilute solution can be approximately treated
as a first order reaction. Therefore, when defining a decomposed
peroxide amount as x, a decomposition rate constant as k, time as
t, and an initial concentration of the organic peroxide as a, the
following mathematical formulae 1, 2 are established.
.times..times..times..times..times..function..times..times..times..times.-
.function..times..times..times..times..times..times.
##EQU00001##
A half-life period is a time required for the initial concentration
of the organic peroxide to halve by decomposition, and hence when t
is defined as a half-life period t.sub.1/2 and a/2 is substituted
into x, a mathematical formula (3) is expressed as follows: ln
2=kt.sub.1/2 Mathematical Formula 3
Accordingly, the organic peroxide is thermally decomposed at some
temperature and a relationship between the time t and ln(a/(a-x))
is plotted and then when k is determined from a gradient k of a
straight line obtained, the half-life period (t.sub.1/2) can be
determined at that temperature by the Mathematical Formula 3.
Silane Coupling Agent
A silane coupling agent used for the silane crosslinking method is
reacted with the above ethylene-propylene random copolymer in the
presence of the radical generator. The silane coupling agent is
expressed by a general formula RR' SiY2 (in the formula, e.g., R
denotes an unsaturated carbon hydride group such as a vinyl group
and an aryl group, or hydrocarbonoxy group; Y denotes a
hydrolyzable organic group such an alkoxyl group or the like
represented by a methoxy group, an ethoxy group, and a butoxy
group; and R' is a substituent group the same as R or Y). In the
general formula, the R part is coupled with the ethylene-propylene
copolymer by the graft reaction, while silanol generated from the Y
part in the formula performs dehydration condensation reaction with
the silanol of the silane coupling agent, coupled to other
ethylene-propylene copolymer, to be crosslinked by siloxane
coupling.
More specifically, as the silane coupling agent, the following
materials are cited: vinyl trimethoxysilane, vinyl triethoxysilane,
vinyl dimethoxymethylslane, vinyl diethoxymethylsilane, vinyl
dimethylethoxysilane, vinyl dimethyethylsilane, vinyl
diethoxyethylsilane, vinyl dimethylmethoxysilane, vinyl
diethylmethoxysilane, vinyl diethylmethoxysilane, vinyl
diethylethoxysilane, vinyl tris(2-methoxyethxy)silane, vinyl
triacetoxysilane, vinyl methyldiacetoxysilane, vinyl
dimethylacetoxysilane, vinyl ethyldiacetoxysilane, vinyl
diethylacetoxysilane, divinyl dimethoxysilane, divinyl
diethoxysilane, divinyl methoxyethoxysilane, divinyl
diacetoxysilane, or the like.
The compounded amount of the silane coupling agent is desirably in
the range of 0.2 to 10 pts. mass, and is more desirably in the
range of 0.5 to 7 pts. mass, and is especially desirably in the
range of 1 to 5 pts. mass, based on 100 pts. mass of the base
resin. If the compounded amount of the silane coupling agent is
less than 0.2 pts. mass, crosslinking points primarily decrease
excessively and then the crosslinked body with a sufficient degree
of crosslinking cannot be obtained. Contrarily, if the compounded
amount of the silane coupling agent is more than 10 pts. mass,
since the concentration of the silane coupling agent heightens
excessively in the system, independent polymerizing reactions and
dehydration condensation reactions increase excessively to make it
impossible to obtain a uniform crosslinked body, thus resulting in
an adverse effect on a physical property of the crosslinked
body.
Silanol Condensation Catalyst
This catalyst is not particularly limited as long as the catalyst
is usable for the silane crosslinking. The following materials are
cited: for example, dibutyltin dilaurate, dibutyltin diacetate,
dibutyltin dioctate, dioctyltin dilaurate, tin(II)octet, tin
naphthenate, zinc caprylate, tetrabutylesther titanate,
tetranonylester titanate, bis(acetylacetonitrile)diisobuyl titanate
or the like. The compounded amount of silanol condensation catalyst
is 0.0005 to 1.0 pts. mass and is desirably 0.01 to 0.5 pts. mass,
based on 100 pts. mass of the base resin. If the compounded amount
of silanol condensation catalyst is less than 0.0005 pts. mass, a
sufficient crosslinking catalyst function cannot be obtained to
laten excessively a crosslinking rate and then a degree of
crosslinking is not fully increased, thereby making a crosslinked
body inferior in rubber property. Contrarily, if the compounded
amount of silanol condensation catalyst is more than 1.0 pts. mass,
a crosslinking function becomes sufficient. This exerts, however,
harmful influences on the mechanical property, the insulating
property if necessary, and other properties, thereby resulting in
an undesirable situation.
Insulating Inorganic Filler
By adding an insulating inorganic filler to the
silane-crosslinkable ethylene-propylene copolymer, the composition
can be obtained where the insulating property is imparted to the
silane-crosslinkable ethylene-propylene copolymer. The insulating
inorganic filler is not especially limited, and the following
materials are cited: calcium carbonate, magnesium hydroxide,
aluminum hydroxide, mica, silica powder, talc, clay, alumina or the
like. These materials may be subjected to surface treatment as
needed. Thus, the above filler can be compounded according to
properties such as an electric property, a mechanical property, and
a flame resistance property required for the products. Further, the
particle diameter of the calcium carbonate is not particularly
limited. An average particle diameter is, however, desirably in the
range of 10 nm to 10 .mu.m, and is more desirably 100 nm or
less.
The compounded amount of this insulating inorganic filler is
desirably in the range of 10 to 150 pts. mass, and is more
desirably in the range of 50 to 100 pts. mass, based on 100 pts.
mass of the base resin. If the compounded amount of the insulating
inorganic filler is less than 10 pts. mass, a sufficient insulating
property cannot be obtained. Contrarily, if the compounded amount
is more than 150 pts. mass, a sufficient insulating property is
possible. The base resin, however, becomes high in hardness, and
hence such harmful influence is exerted on the rubber property such
as a compression set, thereby resulting in an undesirable
situation.
Softener
Further, a softener may be added to the composition containing the
silane-crosslinkable ethylene-propylene copolymer and the
insulating inorganic filler. The softener used for the compositions
according to the present disclosure is not especially limited.
However, a process oil and an aliphatic cyclic saturated
hydrocarbon resin are desirable and the process oil is more
desirable. The process oil is not especially limited as long as it
is generally used as a rubber compounding agent. Then, among
paraffinic, naphthenic, and aromatic oils, one type may be
independently used or, two or more types of the oils are combined
to be usable. In addition, the aliphatic cyclic saturated
hydrocarbon resin is a cyclopentadiene resin or a dicyclopentadiene
resin. Specifically, the aliphatic cyclic saturated hydrocarbon
resin is a petroleum resin composed mainly of cyclopentadiene and
dicyclopentadiene, and means a copolymer composed of the
cyclopentadiene or the dicyclopentadiene and olefin-based
hydrocarbon copolymerizable with the cyclopentadiene and the
dicyclopentadien or means a polymer composed of cyclopentadiene
and/or dicyclopentadiene. An additive amount of and a type of the
softener are not especially limited. The compounded amount of the
softener, however, is desirably 5 to 50 pts. mass and is more
desirably 10 to 30 pts. mass, based on 100 pts. mass of the
insulating inorganic filler. Further, if the compounded amount of
the softener falls below 5 pts. mass, an effect of lowering the
hardness of the composition becomes poor, and contrarily, if the
compounded amount of the softener exceeds 50 pts. mass, a creeping
action and the compression set of the product increase.
Other Components
The resin composition in the present disclosure, in addition to the
above components, an antioxidant, a flame retardant, a
weather-resistant agent, carbon black, a colorant, a filler, and
additive agents such as other stabilizers or the like may be
appropriately compounded. The antioxidant is not especially limited
as long as it is generally usable as the antioxidant and an
anti-aging agent which are typically usable for resin and rubber.
As specific examples, the following materials are cited:
1,3,5-trimethyl-2,4,6-tris(3,5-t-butyl-4-hydroxybenzyl)benzene;
pentaerythrityl-tetrakis[3
(3,5-di-t-butyl-4-hydroxyphenyl)propionate];
2,2,4-trimethyl-1,2-dihydroquinoline polymer;
6-ethoxy-1,2-dihydro-2,2,4-trimethyl quinoline;
N-phenyl-1-naphthylamine; octylateddiphenylamine:
4,4'-bis(.alpha.,.alpha.-dimethylbenzyl)diphenylamine; dilauryl
thiodipropionate; distearylthiodipropionate; dimyristyl
thiodipropionate or the like. These materials are also usable in
combination with one another as may be necessary. The additive
amount of each of the above compounding agents can be appropriately
determined as needed basis within a range of not impairing the
object of the present disclosure.
Manufacturing Method
First Process
A silane compound, the organic peroxide, a reaction auxiliary, the
antioxidant and a processing stabilizer if need arises, an
inorganic filler, and the softener are appropriately compounded
with the above ethylene-propylene random copolymer. An extruder in
which a reaction is possible is employed and then the above
compounded matter is allowed to undergo such processes as melting,
kneading and reacting ones while being heated in the extruder to be
extruded in a strand-like shape, followed by cooling, cutting or
cutting by a rotating blade at an exit of a dice and again cooling
the matter thus cut, thereby obtaining a pellet-like
silane-crosslinkable ethylene-propylene random copolymer (a
silane-modified composition).
Second Process
Further, in a second process, based on the copolymer preliminarily
manufactured in a separate process, a master batch is made by
compounding the silanol condensation catalyst, the antioxidant if
needed, the inorganic filler, and the graphite powder. Then, the
composition is allowed to undergo a melting process and a kneading
process while the composition is being heated inside an injection
molding machine and after injecting the composition into a metallic
mold, the injected matter is rammed down, at a suitable mold
temperature and by a mold compressing pressure, into a product
shape and then is cooled, followed by taking out the cooled matter
and thereafter a crosslinking reaction is advanced at 25.degree. C.
to 95.degree. C. and at an atmospheric humidity under a humidified
environment or inside warm water, thereby enabling a
silane-crosslinked body to be obtained.
Melt Mass-Flow Rate (MFR)
MFR of the silane-modified composition obtained in the first
process increases as compared with MFR of the ethylene-propylene
random copolymer that is a base resin before the silane is
modified. This is because the base resin contains principally the
propylene component, and hence molecular chains are cut during the
reaction to increase the fluidity of the silane-modified
composition. When performing molding by injection molding as is
done in the above example, although MFR of the resin after the
silane is modified is not especially limited, MFR is desirably in
the range of 5.0 to 100.0 g/10 min. in consideration of practical
utility. From this viewpoint, there is a suitable MFR range also
for the ethylene-propylene random copolymer allowed to act as the
base resin and then it is desirable to use MFR of 20.0 g/10 min or
less. If using the resin with a MFR larger than this value, MFR
becomes too high due to a decomposing reaction at the time of
modifying silane, and thereby since a dripping action occurs at the
exit of the dice and the viscosity of the resin is enhanced, a
pelletizing process become impossible to cause a defect in
handling, making it impossible to supply the materials to the
subsequent process. Additionally, in order to obtain the
silane-crosslinkable resin excellent in fluidity, it is especially
desirable that the MFR of the resin is 2.5 g/10 min. or more.
Average Molecular Weight
In order to minimize an adverse effect on the physical property
caused by cutting the molecular chains due to decomposition, there
is a suitable range also for an average molecular weight of the
base resin. The standard polystyrene conversion weight-average
molecular weight obtained by a measuring method shown below is
desirably 15,000 to 5,000,000. More desirably, the weight-average
molecular weight is in the range of 30,000 to 2,000,000. In the
same fashion as MFR, if the weight-average molecular weight exceeds
5,000,000, a silane-crosslinkable resin excellent in fluidity
cannot be obtained, and contrarily if the weight-average molecular
weight falls below 15,000, such a problem is posed that a defect
occurs in handling the resin, and therefore the materials cannot be
supplied to the subsequent process.
Method for Measuring Molecular Weight
A high temperature GPC device (PL-220 made by Polymer Laboratories,
Column: two PLgel MIXED-BLSs) with a differential refractive index
detector was employed. As a solvent, orthodichlorobenzene was used.
The solvent may contain a small amount of a stabilizer (such as
BHT) if needed. Resin of 10 mg was put in in regard to the solvent
of 5 mL and then the solution was agitated while applying heat till
the resin was completely solved. The sample solution thus
conditioned was injected into a testing machine with capacity of
0.200 mL. Then, a dissolution curve was measured at the flow rate
of 1.0 mL/min. and at the column temperature of 145.degree. C. As
the standard sample, monodisperse polystyrene was used and the
molecular weight calculated by the data processing was a
polystyrene conversion value.
Effects According to the Present Embodiments
According to the present embodiments, there can be provided the
crosslinked body with a recovery property after applying tension,
the rubber property such as flexibility, an insulating property, an
electrical property such as a tracking resistance property, a heat
resistance property, a long-term property such as a heat aging
resistance property, and a high degree of freedom for a composition
for the sake of corresponding flexibly to the levels demanded for
the above properties.
By obtaining the above crosslinked body using the silane
crosslinking method, without requiring an independent vulcanizing
process or a crosslinking process, the manufacturing time can be
reduced and thereby the manufacturing cost can be considerably
decreased with high productivity kept. Specifically, in the
silane-crosslinking method according to the present embodiment,
without the need to establish an independent crosslinking process,
the silane crosslinking process proceeds during a molding process,
thus permitting the rubber property to be obtained.
EXAMPLES
Next, in order to further clarify the effects of the present
disclosure, examples and comparative examples are described in
detail. The present disclosure, however, is not limited to these
examples.
Example 1
Graft Modification Process
The ethylene-propylene copolymer, whose propylene component was 85%
by mass, and MFR measured at 230.degree. C. and with a load of 2.16
kg applied is 20 g/10 min and which was a random copolymer with an
isostatic structure, was injected into a twin-screw extruder with a
screw diameter of 15 mm and L/D=45. While injecting, from a liquid
adding vent provided in an intermediary portion of a barrel, a
mixed solution of vinyltrimethoxysilane (VTMS) and
peroxy-cyclohexane acid 1,1-t-butyl (one-minute half-life
temperature was 153.8.degree. C.) at the rate of 2.0 pts. mass and
0.23 pts. mass, respectively per 100 pts. mass of the resin so that
this rate was kept constant by a gear pump; the mixed solution was
extruded into a strand-like shape with the temperature of a strand
die set at 185.degree. C. By allowing the strand-like matter to
undergo a cooling process and a cutting process, a pellet-like
silane-crosslinkable ethylene-propylene copolymer was obtained.
Catalyst Mixing, Sheeting, and Crosslinking Process
0.05 pts. mass of the dibutyltin dilaurate was mixed per 100 pts.
mass of the pellet-like silane-crosslinkable ethylene-propylene
copolymer thus obtained. This mixture was injected into a roll
device whose surface temperature was set at 65.degree. C. in
advance. After kneading the mixture for 5 minutes, a gap between
the rolls was adjusted to become approximately 2 mm according to
the thickness of a sheet and the rolled strips were taken out.
After cutting the strips in conformity to a mold which was 200 mm
long, 160 mm wide and 2 mm thick, the strips were put in a press
machine whose press plate was set at 130.degree. C. in advance and
then was pressed by 5 MPa pressure for five minutes to be cooled to
30.degree. C. or less without any change, thus making a sheet which
was 200 mm long, 160 mm wide and 2 mm thick. The sheet thus
obtained was immersed in warm water of 80.degree. C. for 24 hours,
thus obtaining a crosslinked body according to the example 1.
Example 2
Except for changing the amounts of the vinyltrimethoxysilane and
the peroxy-cyclohexane acid 1,1-t-butyl into those as listed in a
Table 1, the crosslinked body was made by the same method as that
in the example 1.
Examples 3 to 9
Except for changing a type of the base resin into one whose
propylene component was 84% by mass and MFR was 2.5 g/10 min., and
the amounts of the vinyltrimethoxysilane and the peroxy-cyclohexane
acid 1,1-t-butyl into those as listed in the Table 1, the
crosslinked bodies were made by the same method as that in the
example 1.
Example 10
Except for changing the organic peroxide into dibenzoyl peroxide
(one-minute half-life temperature was 130.0.degree. C.) and a
compounded amount of the dibenzoyl peroxide into that as listed in
the Table 1, the crosslinked body was made by the same method as
that in the example 1.
Example 11
Except for changing the silane coupling agent into the
vinyltriethoxysilane (VTES) and the amount of the
vinyltriethoxysilane into that as listed in the Table 1, the
crosslinked body was made by the same method as that in the example
3.
Example 12
Except for changing a type of the base resin into one whose
propylene component was 75 mass % and MFR was 5 g/10 min., and the
amount of the peroxy-cyclohexane acid 1,1-t-butyl into that as
listed in the Table 1, the crosslinked body was made by the same
method as that in the example 1.
Example 13
Except for changing the organic peroxide into the dicumyl peroxide
(one-minute half-life temperature was 175.2.degree. C.), and the
amounts of the vinyltrimethoxysilane and the organic peroxide into
those as listed in the Table 1, the crosslinked body was made by
the same method as that in the example 3.
Examples 14 to 17
Graft Modification Process
The ethylene-propylene copolymer, whose propylene component was 84%
by mass and MFR measured at 230.degree. C. and with a load of 2.16
kg applied was 2.5 g/10 min and which was a random copolymer with
the isotactic structure, was injected into the twin-screw extruder
with the screw diameter of 15 mm and L/D=45. The mixed solution of
the vinyltrimethoxysilane (VTMS) and the peroxy-cyclohexane acid
1,1-t-butyl (one-minute half-life temperature was 153.8.degree. C.)
was injected at the rate of 2.0 pts. mass and 0.32 pts. mass,
respectively, per 100 pts. mass of the resin, from the liquid
adding vent provided in the intermediary portion of the barrel so
that this rate was kept constant by a gear pump. Further, calcium
carbonate of the compounded amount as listed in a Table 3 was
injected into the extruder so that this compounded amount was kept
constant by a coil feeder, and then the mixed matter was pushed out
into a strand-like shape with a strand die set at 185.degree. C. By
allowing the strand-like matter to undergo a cooling process and a
cutting process, pellet-like silane-crosslinkable
ethylene-propylene copolymers were obtained.
Catalyst Mixing, Sheeting, and Crosslinking Process
0.05 pts. mass of the dibutyltin dilaurate was mixed per 100 pts.
mass of the pellet-like silane-crosslinkable ethylene-propylene
copolymer thus obtained. Further, carbon black, a compatibilizing
agent, and an anti-aging agent were mixed in the compound amounts
as listed in the Table 3. Then, this mixture was injected into a
roll device whose surface temperature was set at 65.degree. C. in
advance. After kneading the mixture for 5 minutes, a gap between
the rolls was adjusted to become approximately 2 mm according to
the thickness of a sheet and the rolled strips were taken out.
After cutting the strips in conformity to a mold which was 200 mm
long, 160 mm wide and 2 mm thick, the strips were put in a press
machine whose press plate was set at 130.degree. C. in advance, and
then was pressed by 5 MPa pressure for five minutes to be cooled to
the temperature less than 30.degree. C. without any change, thus
making a sheet which was 200 mm long, 160 mm wide and 2 mm thick.
The sheet thus obtained was immersed in warm water of 80.degree. C.
for 24 hours, thus obtaining the crosslinked bodies according to
the examples 14 to 17.
Examples 18 to 25
Graft Modification Process
The ethylene-propylene copolymer, whose propylene component was 84
mass % and MFR measured at 230.degree. C. and with a load of 2.16
kg applied was 2.5 g/10 min. and which was a random copolymer with
an isostatic structure, was injected into the twin screw extruder
with the screw diameter of 15 mm and L/D=45. From the first liquid
adding vent provided in the intermediary portion of the barrel, the
mixed solution of the vinyltrimethoxysilane (VTMS) and the
peroxy-cyclohexane acid 1,1-t-butyl (one-minute half-life
temperature was 153.8.degree. C.) was injected at the rate of 2.0
pts. mass and 0.32 pts. mass, respectively per 100 pts. mass of the
resin so that that this rate was kept constant by the gear pump.
Further, calcium carbonate of the compounded amount as listed in a
Table 3 was injected into the extruder so that this compounded
amount of the calcium carbonate was kept constant by the coil
feeder. Furthermore, a process oil of the compounded amount as
listed in the Table 3 was injected from the second liquid adding
vent provided in the intermediary portion of a barrel on a dice
side nearer than the side feeder so that the rate of the process
oil is kept constant by the gear pump. Then the compounded matter
was extruded into a strand-like shape with a strand die set at
185.degree. C. After allowing the strand-like matter to undergo a
cooling process and a cutting process, a pellet-like
silane-crosslinkable ethylene-propylene copolymers were
obtained.
Catalyst Mixing, Sheeting, and Crosslinking Process
0.05 pts. mass of the dibutyltin dilaurate was mixed per 100 pts.
mass of the pellet-like silane-crosslinkable ethylene-propylene
copolymer thus obtained. Further, carbon black, the compatibilizing
agent, and the anti-aging agent were mixed in the compound amounts
as listed in the Table 3. This mixture was injected into a roll
device whose surface temperature was set at 65.degree. C. in
advance. After kneading the mixture for 5 minutes, the gap between
the rolls was adjusted to become approximately 2 mm according to
the thickness of the sheet and the rolled strips were taken out.
After cutting the strips in conformity to a mold which was 200 mm
long, 160 mm wide and 2 mm thick, the strips were put in a press
machine whose press plate was set at 130.degree. C. in advance and
then was pressed by 5 MPa pressure for five minutes to be cooled to
the temperature less than 30.degree. C. without any change, thus
making a sheet which was 200 mm long, 160 mm wide and 2 mm thick.
The sheet thus obtained was immersed in warm water of 80.degree. C.
for 24 hours, thus obtaining crosslinked bodies according to the
examples 18 to 25.
Example 26
Except for changing, in the graft process, the softener into the
aliphatic cyclic saturated hydrocarbon resin, and a feeding method
into one where the compounded amount of the aliphatic cyclic
saturated hydrocarbon resin as listed in the Table 3 underwent a
dry blend with the ethylene-propylene copolymer from a hopper
section to be injected so that the rate of the compounded amount of
the aliphatic cyclic saturated hydrocarbon resin was kept constant,
the crosslinked bodies were made by the same method as those in the
examples 18 to 25.
Comparative Examples 1 and 2
Except for changing the compounded amounts of the
vinyltrimethoxysilane and the peroxy-cyclohexane acid 1,1-t-butyl
into those as listed in a Table 2, the crosslinked bodies were made
by the same method as that in the example 3.
Comparative Example 3
Except for changing the organic peroxide into di-t-butyl peroxide
(one-minute half-life temperature was 185.9.degree. C.) and the
compounded amount of the organic peroxide into that as listed in
the Table 2, the crosslinked body was made by the same method as
that in the example 1.
Comparative Example 4
Except for changing a type of the base resin into one whose
propylene component was 96% by mass, the crosslinked body was made
by the same method as that in the example 1.
Method for Measuring Various Parameters Listed in Table
The component amount of the polypropylene of the base resin, the
melt mass flow rate (MFR), the type of silane coupling agent, the
amount of silane coupling agent, the one-minute half-life
temperature of the organic peroxide, and the amount of the organic
peroxide are listed in the Tables.
(1) Amount of Propylene Component
A composition of the ethylene-propylene copolymer is determined as
a mass percent of the propylene by measuring a mass percent of the
ethylene according to ASTM D3900 as below and then subtracting the
measured value of the mass percent of the ethylene from 100. A
homogeneous film of the present polymer component pressed at
150.degree. C. or more is fitted on an infrared spectrophotometer
(Nicolet MAGNA550). A perfect spectrum of the sample ranging from
600 cm-1 to 4,000 cm-1 is recorded and the mass percent of the
ethylene of the copolymer component is calculated from the formula
expressed by Mass % of the ethylene=82.585-111.987X+30.045X2,
wherein in the formula, X denotes a ratio of a peak height of 1155
cm.sup.-1 to a higher peak height in the peak heights of 722
cm.sup.-1 and 732 cm.sup.-1.
(2) MFR
The MFR is a value measured by a method pursuant to the condition,
that test temperature is 230.degree. C. and a test load is 2.1 6
kg, based on "MFR of Plastic-Thermoplastic Plastic and Melt Volume
Flow Rate I (MVR)" according to JIS K 7210.
(3) "Method for Measuring One-Minute Half-Life Temperature of
Organic Peroxide"
The method of the one-minute half-life temperature of the organic
peroxide is as described above.
Method for Evaluating Various Measured Results Listed in Table
The evaluation was conducted for the following items of the
crosslinked sheets thus obtained.
(1) Heat Deformation Ratio of Crosslinked Sheet
The heat deformation ratio of the crosslinked body is measured by a
method pursuant to a method h for measuring a heat deformation
ratio in "Method for Testing Rubber or Plastic-Insulated Cable"
according to JIS C 3005. Specifically, the sheet-like test piece of
the crosslinked body (2 mm thick, about 15 mm wide, and about 30 mm
long) is put in a test machine heated to 100.degree. C. in advance
and after heating the test piece for 30 minutes therein, the test
piece is laid on a place between parallel plates of the measuring
device and then a load of 2.0 kgf was applied to the test piece and
further after 30 minutes at the same temperature, the thickness t1
of the test piece was measured just as it is and the heat
deformation ration is calculated as a reduction ratio from the
thickness t1 after heating and the thickness t0 before heating.
X=(t.sub.0-t.sub.1)/t.sub.0*100
wherein X is the reduction ratio (%), t.sub.0 is the thickness
before heating (mm), t.sub.1 is the thickness after heating (mm).
The heat deformation ratio of 35% or less is permissible.
(2) Residual Strain Ratio
A residual strain ratio is determined in the following fashion. A
rectangular test piece of the crosslinked body (thickness: 2 mm,
width: 10 mm, and length: 50 mm except for a length of the
grippers) is put into a test machine heated to 90.degree. C. in
advance. After heating the sample for 5 minutes, an initial setting
(a) described below is carried out to determine a length of the
crosslinked body before a tensile test. Then, after extending the
crosslinked body at a tension rate of 50 mm/min. inside the test
machine until the strain ratio reaches 250%, the crosslinked body
is immediately recovered at a speed of 50 mm/min to measure a
distance between grippers at the moment the stress becomes 0 pa.
Thus, the residual strain ratio is determined according to the
following formula, from this length l.sub.1 h after applying
tension and a length l.sub.0 before applying tension.
Y=(l.sub.1-l.sub.0)/l.sub.0*100,
wherein Y is the tensile residual strain ratio (%), l.sub.0 is the
length before applying tension (mm), and l.sub.1 is the length
after applying tension (mm).
Initial Setting (a)
After preheating the test piece at 90.degree. C. for 5 minutes, the
crosslinked body is held in upper and lower grippers (an interval
between the both is 50 mm) of the tensile testing machine, and
thereafter such an operation is performed that a distance between
the upper and lower grippers at the time of removing a deflection
till the stress reaches 17.5 kPa at the tension rate of 5.0 mm/min.
or less is defined as the length before applying the tension.
The residual strain ratio of 60% or less is permissible and that of
40% or less is more desirable.
(3) Hardness
Using a sample of 80 mm.times.50 mm.times.6 mm, the hardness was
measured with a hardness tester (JIS A) pursuant to JIS K6253. The
hardness of 85 or less is permissible.
(4) Compression Set
The compression set is a value measured in conformity to JIS K6262.
Specifically, a test piece which is 29.0 mm across and 12.5 mm
thick is cut off and then the thickness at this time was exactly
measured as the original thickness of the test piece. Next, the
thickness of this test piece was compressed by 25% to be fixed and
then was left at 100.degree. C. for 70 hours. Afterward, the test
piece was detached and after leaving the test piece for 30 min, the
compression set was calculated by the following formula. The
compression set of 60% or more is permissible. Compression set
(%)={the original thickness (mm) of the test piece-the thickness of
the test piece after the test}/{the original thickness (mm) of the
test piece (mm)-the thickness of a spacer (mm)}*100
(5) Resistance to Tracking
A test piece of 50 mm.times.120 mm.times.6 mm is made. The surface
of the test piece is polished with an abrasive paper of #2000 until
the grazing of the surface disappears. According to JIS C2136, a
contaminating liquid (ammonia water) is started to be supplied (0.3
ml/min.) onto the surface of the test piece made above and with the
contaminating liquid allowed to flow constantly there-onto, a
voltage is boosted up to 3.5 kV to measure a time required to cause
its dielectric breakdown. If the dielectric breakdown is generated
within or beyond 360 minutes, a mark x or a mark .smallcircle. is
recorded, respectively.
(6) AC Breakdown
A discoidal test piece 1 mm thick is made according to JIS C2110-1.
Electrodes were set at an approximately central portion of the test
piece between upper and lower portions of the test piece. An AC
voltage is boosted from 0 V at a constant rate (1 kV/10 min.) and
thus an AC breakdown voltage is measured. The AC breakdown strength
is determined by the following formula. The AC dielectric breakdown
strength of 25 k V/mm or more is permissible. AC dielectric
breakdown strength (kV/mm)=AC dielectric breakdown voltage
(kV)/thickness of test piece (mm)
The details of each of the components in the compositions used in
the examples and the comparative examples are as shown below.
Resin Component
EP elastomer (ethylene-propylene copolymer)
Propylene content=85%
MFR=20 g/10 min.
EP elastomer (ethylene-propylene copolymer)
Propylene content=84%
MFR=2.5 g/10 min.
EP elastomer (ethylene-propylene copolymer)
Propylene content=75%
MFR=5 g/10 min
EP elastomer (ethylene-propylene copolymer)
Propylene content=96%
MFR=2.5 g/10 min
Silane Coupling Agent
Trade name: SZ-6300 made by Toray Dow Corning Co., Ltd.
Organic Peroxide
Trade name: Perhexa C made by NOF Corporation
Insulating Inorganic Filler
Calcium carbonate: Trade name: Shirotsuya-ka CC made by Shiraishi
Calcium Kaisha Ltd.
Softener
Paraffinic Oil Trade name: PW-380 made by Idemitsu Petroleum Co.,
Ltd.
Aromatic cyclic saturated hydrocarbon resin, Trade name: Alcon
P-100 made by Arakawa Chemical Industries, Ltd.
Carbon Black
Trade name: Carbon black #3H made by Tokai Carbon Co., Ltd.
Compatibilizer
Trade name: Powder Stearic Acid made by NOF Corporation,
Anti-Aging Agent
Trade Name: Nocrac MB made by Ouchi-Shinko chemical Industrial Co.,
Ltd.
The above results are shown in the following Tables.
TABLE-US-00001 TABLE 1 Example Example Example Example Example
Example Example 1 2 3 4 5 6 7 Polypropylene 85 85 84 84 84 84 84
component [% by mass] MFR [g/10 min] 20 20 2.5 2.5 2.5 2.5 2.5 Type
of Silane VTMS VTMS VTMS VTMS VTMS VTMS VTMS Silane amount 2 5 1 1
2 2 2 [pts. Mass] T.sub.h1 of peroxide 153.8 153.8 153.8 153.8
153.8 153.8 153.8 [.degree. C.] Peroxide amount 0.23 0.32 0.32 0.57
0.1 0.32 0.6 [pts. mass] Heat Deformation 35 28.9 22.1 20.3 26.4
24.4 14.6 ratio [%] Residual strain 34.7 28.9 28.7 28.7 39.5 30.5
21.4 ratio [%] Example Example Example Example Example Example 8 9
10 11 12 13 Polypropylene 84 84 85 84 75 84 component [% by mass]
MFR [g/10 min] 2.5 2.5 20 2.5 5 2.5 Type of Silane VTMS VTMS VTMS
VTES VTMS VTMS Silane amount 5 5 5 5 2 2 [pts. mass] T.sub.h1 of
peroxide 153.8 153.8 130.0 153.8 153.8 175.2 [.degree. C.] Peroxide
amount 0.12 0.32 0.36 0.32 0.32 0.27 [pts. mass] Heat Deformation
25.3 16.6 29 25.8 26.9 22.3 ratio [%] Residual strain 37.3 28.4
35.6 33.8 21.6 29.8 ratio [%]
TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative example 1 example 2 example 3 example 4 Polypropylene
84 84 85 96 component [% by mass] MFR 2.5 2.5 20 2.5 [g/10 min]
Type of Silane VTMS VTMS VTMS VTMS Silane amount 5 1 2 2 [pts.
mass] T.sub.h1 of peroxide 153.8 153.8 185.9 153.8 [.degree. C.]
Peroxide 0.65 0.09 0.18 0.23 amount [pts. mass] Heat 13.4 40.3 23 4
Deformation ratio [%] Residual strain broken 42.8 broken broken
ratio [%]
TABLE-US-00003 TABLE 3 Example Example Example Example Example
Example Example Composition 14 15 16 17 18 19 20 Polypropylene 84
84 84 84 84 84 84 component [% by mass] MFR [g/10 min] 2.5 2.5 2.5
2.5 2.5 2.5 2.5 Type of Silane VTMS VTMS VTMS VTMS VTMS VTMS VTMS
Silane amount [pts. 2 2 2 2 2 2 2 Mass] T.sub.h1 of peroxide
[.degree. C.] 153.8 153.8 153.8 153.8 153.8 153.8 153.8 Peroxide
amount [pts. 0.32 0.32 0.32 0.32 0.32 0.32 0.32 mass] Calcium
carbonate 10 50 100 150 10 50 100 amount [pts. mass] Softener
Process oil 0 0 0 0 5 5 5 [pts. mass Aromatic 0 0 0 0 0 0 0 per 100
Cyclic pts of saturated Calcium hydrocarbon carbonate] resin Carbon
black [pts. mass] 1 1 1 1 1 1 1 Compatibilizer [pts. 2 2 2 2 2 2 2
mass] Anti-aging agent [pts. 1.3 1.3 1.3 1.3 1.3 1.3 1.3 mass] Heat
distortion ratio [%] 20.5 17.3 14.4 11.7 22.3 18.9 15.4 Residual
strain ratio [%] 30.2 39.1 43.1 47.5 34.3 39.5 4.26 Hardness 64.6
70.3 72.5 81.6 62.1 63.5 75 Compression set [%] 28.1 29.4 30.5 41.4
29.3 31.3 44.7 Resistance to tracking AC dielectric breakdown 25.3
27.6 30.2 45 27.4 29.1 32.2 strength [kV/mm Example Example Example
Example Example Example Composition 21 22 23 24 25 26 Polypropylene
84 84 84 84 84 84 component [% by mass] MFR [g/10 min] 2.5 2.5 2.5
2.5 2.5 2.5 Type of Silane VTMS VTMS VTMS VTMS VTMS VTMS Silane
amount [pts. 2 2 2 2 2 2 Mass] T.sub.h1 of peroxide [.degree. C.]
153.8 153.8 153.8 153.8 153.8 153.8 Peroxide amount [pts. 0.32 0.32
0.32 0.32 0.32 0.32 mass] Calcium carbonate 100 100 100 150 150 100
amount [pts. mass] Softener Process Oil 10 30 50 10 50 0 [pts. mass
Aromatic 0 0 0 0 0 30 per 100 Cyclic pts of saturated Calcium
hydrocarbon carbonate] resin Carbon black [pts. mass] 1 1 1 1 1 1
Compatibilizer [pts. 2 2 2 2 2 2 mass] Anti-aging agent [pts. 1.3
1.3 1.3 1.3 1.3 1.3 mass] Heat distortion ratio [%] 17.8 22.1 25.4
12.3 19.8 13.1 Residual strain ratio [%] 45.3 46.1 47.9 49.3 53.3
42.6 Hardness 72.5 62.5 52.5 79.6 59.6 63.8 Compression set [%]
46.3 49.7 52.3 51.3 57 31.3 Resistance to tracking AC dielectric
breakdown 34.7 37.3 42.8 46.2 49.7 36.9 strength [kV/mm
In the example 1 and the example 12, the base resins considerably
different in the propylene contents were used. In both the
examples, the propylene component amount of the propylene copolymer
resin, MFR, the compounded amounts of the organic peroxide and the
silane coupling agent in regard to the propylene copolymer resin,
and the one-minute half-life temperature of the organic peroxide
fall within the predetermined range and therefore both the examples
satisfy a target performance with respect to each of the evaluation
items after the crosslinking reaction.
In the example 1 and the example 6, the base resins different
considerably in MFR were used. Since the value of MFR lies between
2.5 and 20.0 g/10 min., both the examples satisfy a target
performance in regard to each of the evaluation items after the
crosslinking reaction.
In the example 2, the example 10 and the example 13, the organic
peroxides different considerably in the one-minute half-life
temperature were used. Since the one-minute half-life temperatures
of the organic peroxides lie between 130 and 176.degree. C., these
examples satisfy a target performance in regard to each of the
evaluation items after the crosslinking reaction.
In the example 9 and the example 11, the silane coupling agents
different in type were used. Even in using any type of the silane
coupling agents, both the examples satisfy a target performance in
regard to each of the evaluation items after the crosslinking
reaction.
In the example 5 and the example 7, the amounts of the organic
peroxide are different considerably from each other. In both the
examples, since the compounded amounts of the organic peroxide are
in the range of 0.1 to 0.6 pts. mass based on 100 pts. mass of the
ethylene-propylene copolymer resin, both the examples satisfy a
target performance in regard to each of the evaluation items after
the crosslinking reaction.
In the example 2 and the example 3, the amounts of the silane
coupling agent are different considerably from each other. In both
the examples, since the amount of the silane coupling agent is in
the range of 1 to 5 pts. mass based on 100 pts. mass of the
ethylene-propylene copolymer resin, both the examples satisfy a
target performance in regard to each of the evaluation items after
the crosslinking reaction.
In examples 14 to 25, the compounded amounts of the insulating
inorganic filler or the process oil are different from each other.
Since the calcium carbonate is 10 to 150 pts. mass based on 100
pts. mass of the silane-crosslinkable ethylene-propylene copolymer
and further the process oil is in the rage of 5 to 50 pts. mass
based on 100 pts. mass of the calcium carbonate, these examples
satisfy a target performance in regard to each of the evaluation
items after the crosslinking reaction.
In the example 26, the aliphatic cyclic saturated hydrocarbon resin
was used in substitution for the process oil. Even in using the
same compounded amount as those described in the examples 18 to 25,
the example satisfies a target performance in regard to each of the
evaluation items after the crosslinking reaction.
In the comparative example 1, since the organic peroxide was
excessive in amount, the base resin made excessive progress in
decomposition to become unendurable for the deformation of 250% at
the time of measuring the residual strain ratio and hence was
broken.
In the comparative example 2, since the organic peroxide is too low
in amount, the crosslinking reaction was not fully progressed, and
then the heat deformation ratio after the crosslinking reaction
exceeded 40%.
In the comparative example 3, since the one-minute half-life
temperature of the organic peroxide was too high, the resin made
excessive progress in decomposition at the time of extruding to
become unendurable for the deformation of 250% at the time of
measuring the residual strain ratio and hence was broken.
In the comparative example 4, the component of the propylene of the
ethylene-propylene copolymer was excessive in amount, the
rubber-like property was poor in the resin itself, and hence at the
time of measuring the residual strain ratio, not only the recovery
motion did not occur after applying tension but the resin was
broken in mid-course of the measurement.
As above, the preferred embodiments of the present disclosure have
been described. The present disclosure is not limited to the above
embodiments according to the present disclosure. Those skilled in
the art obviously can make various altered embodiments and various
modifications within the scope of the technical idea disclosed in
this application. Hence, these various altered embodiments and
various modifications can be definitely considered to fall within
the technical scope of the present disclosure.
* * * * *
References